[Spice-devel] [PATCH spice-gtk v2] spice-gtk: Use time comparisons that still work after wraparound
Christophe de Dinechin
dinechin at redhat.com
Tue Jul 18 14:37:29 UTC 2017
>
> On 17 Jul 2017, at 14:20, Christophe Fergeau <cfergeau at redhat.com> wrote:
>
> On Mon, Jul 17, 2017 at 02:00:01PM +0200, Christophe de Dinechin wrote:
>>
>>> On 17 Jul 2017, at 13:49, Christophe Fergeau <cfergeau at redhat.com <mailto:cfergeau at redhat.com>> wrote:
>>>
>>> On Mon, Jul 17, 2017 at 11:44:04AM +0200, Christophe de Dinechin wrote:
>>>> From: Christophe de Dinechin <dinechin at redhat.com <mailto:dinechin at redhat.com>>
>>>>
>>>> The mm timer is a millisecond timer that wraps around after ~49 days.
>>>> All comparisons that look like a<b will fail once this happens.
>>>> Instead, use signed ((int)(a-b)<0), which may fail if there is more than
>>>> 25 days between a and b (should not be happening under normal conditions),
>>>> but is robust to the timer wrapping around.
>>>>
>>>> Signed-off-by: Christophe de Dinechin <dinechin at redhat.com <mailto:dinechin at redhat.com>>
>>>> ---
>>>> src/channel-display-gst.c | 4 ++--
>>>> src/channel-display-mjpeg.c | 4 ++--
>>>> src/channel-display.c | 2 +-
>>>> src/channel-playback.c | 2 +-
>>>> src/spice-channel-priv.h | 2 ++
>>>> src/spice-session.c | 4 ++--
>>>> 6 files changed, 10 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/src/channel-display-gst.c b/src/channel-display-gst.c
>>>> index adcd6ef..3f51361 100644
>>>> --- a/src/channel-display-gst.c
>>>> +++ b/src/channel-display-gst.c
>>>> @@ -166,7 +166,7 @@ static void schedule_frame(SpiceGstDecoder *decoder)
>>>> break;
>>>> }
>>>>
>>>> - if (now < gstframe->frame->mm_time) {
>>>> + if (spice_mmtime_diff(now, gstframe->frame->mm_time) < 0) {
>>>> decoder->timer_id = g_timeout_add(gstframe->frame->mm_time - now,
>>>> display_frame, decoder);
>>>> } else if (g_queue_get_length(decoder->display_queue) == 1) {
>>>> @@ -511,7 +511,7 @@ static gboolean spice_gst_decoder_queue_frame(VideoDecoder *video_decoder,
>>>> return TRUE;
>>>> }
>>>>
>>>> - if (frame->mm_time < decoder->last_mm_time) {
>>>> + if (spice_mmtime_diff(frame->mm_time, decoder->last_mm_time) < 0) {
>>>> SPICE_DEBUG("new-frame-time < last-frame-time (%u < %u):"
>>>> " resetting stream",
>>>> frame->mm_time, decoder->last_mm_time);
>>>> diff --git a/src/channel-display-mjpeg.c b/src/channel-display-mjpeg.c
>>>> index ee33b01..3ba098c 100644
>>>> --- a/src/channel-display-mjpeg.c
>>>> +++ b/src/channel-display-mjpeg.c
>>>> @@ -201,7 +201,7 @@ static void mjpeg_decoder_schedule(MJpegDecoder *decoder)
>>>> decoder->cur_frame = NULL;
>>>> do {
>>>> if (frame) {
>>>> - if (time <= frame->mm_time) {
>>>> + if (spice_mmtime_diff(time, frame->mm_time) <= 0) {
>>>> guint32 d = frame->mm_time - time;
>>>> decoder->cur_frame = frame;
>>>> decoder->timer_id = g_timeout_add(d, mjpeg_decoder_decode_frame, decoder);
>>>> @@ -251,7 +251,7 @@ static gboolean mjpeg_decoder_queue_frame(VideoDecoder *video_decoder,
>>>>
>>>> last_frame = g_queue_peek_tail(decoder->msgq);
>>>> if (last_frame) {
>>>> - if (frame->mm_time < last_frame->mm_time) {
>>>> + if (spice_mmtime_diff(frame->mm_time, last_frame->mm_time) < 0) {
>>>> /* This should really not happen */
>>>> SPICE_DEBUG("new-frame-time < last-frame-time (%u < %u):"
>>>> " resetting stream",
>>>> diff --git a/src/channel-display.c b/src/channel-display.c
>>>> index 3c98d79..06ed18a 100644
>>>> --- a/src/channel-display.c
>>>> +++ b/src/channel-display.c
>>>> @@ -1366,7 +1366,7 @@ static void display_update_stream_report(SpiceDisplayChannel *channel, uint32_t
>>>> }
>>>>
>>>> if (st->report_num_frames >= st->report_max_window ||
>>>> - now - st->report_start_time >= st->report_timeout ||
>>>> + spice_mmtime_diff(now - st->report_start_time, st->report_timeout) >= 0 ||
>>>> st->report_drops_seq_len >= STREAM_REPORT_DROP_SEQ_LEN_LIMIT) {
>>>> SpiceMsgcDisplayStreamReport report;
>>>> SpiceSession *session = spice_channel_get_session(SPICE_CHANNEL(channel));
>>>> diff --git a/src/channel-playback.c b/src/channel-playback.c
>>>> index ca14b96..afc9059 100644
>>>> --- a/src/channel-playback.c
>>>> +++ b/src/channel-playback.c
>>>> @@ -313,7 +313,7 @@ static void playback_handle_data(SpiceChannel *channel, SpiceMsgIn *in)
>>>> packet->time, packet->data, packet->data_size);
>>>> #endif
>>>>
>>>> - if (c->last_time > packet->time)
>>>> + if (spice_mmtime_diff(c->last_time, packet->time) > 0)
>>>> g_warn_if_reached();
>>>>
>>>> c->last_time = packet->time;
>>>> diff --git a/src/spice-channel-priv.h b/src/spice-channel-priv.h
>>>> index 7288920..20d3495 100644
>>>> --- a/src/spice-channel-priv.h
>>>> +++ b/src/spice-channel-priv.h
>>>> @@ -43,6 +43,8 @@ G_BEGIN_DECLS
>>>> #define CHANNEL_DEBUG(channel, fmt, ...) \
>>>> SPICE_DEBUG("%s: " fmt, SPICE_CHANNEL(channel)->priv->name, ## __VA_ARGS__)
>>>>
>>>> +#define spice_mmtime_diff(now, time) ((int32_t) ((now)-(time)))
>>>
>>> Nit: I think the 'now' and 'time' naming here could be misleading, what
>>> about just "mmtime0" and "mmtime1" for example?
>>
>> Well, that was to match the typical usage where ‘now’ would be the
>> current time, and ‘time’ would be some other reference time. To me,
>> that’s more readable that way. But YMMV…
>
> Dunno, looking at spice_mmtime_diff(c->last_time, packet->time), none of
> the args strike me as the obvious "current" time. And the function is
> generic, spice_mmtime_diff(old_time, current_time) would work equally
> well as spice_mmtime_diff(current_time, old_time). So the "now" name
> seems very artificial to me.
OK. Since you seem to feel more strongly about this than me, I changed it.
Pushed to freedesktop.org. Since this is the first time I push myself to this repo,
would you please be kind enough to check that what I pushed looks sane?
Thanks
Christophe
>
> Christophe
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